1. Field of Use
This invention relates generally to high-speed automatic storage and retrieval systems (AS/RS) which employ stationary storage racks, aisle cranes (AS/R), automatic guided vehicles (AGV), and control means therefor.
2. Description of the Prior Art
Such systems are used in factories and warehouses to enable objects or materials produced (or received) at an entry location to be temporarily stored in compartments in the storage racks prior to delivery to an exit location for transport elsewhere (i.e., inside or outside the factory or warehouse). The objects or materials may be manufactured parts or various other products or may be containers filled with such parts or products. The compartments in the storage racks are adapted, as the situation requires, to receive and directly support parts or products of particular configuration (i.e., such as large automobile subassemblies) or to receive and support containers filled with parts or products. Typically, the object or load is loaded onto an automatic guided vehicle at the entry location and automatically transported thereby along a rail network to the end of an aisle in which a self-propelled aisle crane is located. The crane has an extendable/retractable shuttle thereon, which receives the object or load from the AGV and stores it in a storage rack compartment. When needed, the aisle crane retrieves the object or load from the compartment and delivers it to an empty available automatic guided vehicle at the end of an aisle which transports it to the exit location.
In some factories, parts or sub-assemblies are produced at one location and are temporarily stored in storage racks until needed at some other location where they are further processed or installed in larger assemblies. The ability to maintain a buffer inventory in temporary storage accommodates differences between production rates and installation rates, facilitates better scheduling and product flow and reduces idle inventory.
Important considerations in the design and arrangement of such systems and apparatus are: economical use of rack floor space, aisle space and overhead space; economical use of time in transporting, storing and retrieving the objects; ability to quickly identify and retrieve various types of objects which are stored in various compartments (use of "first-in-first-out" and "last-in-last-out" inventory concepts is one solution); minimizing the time and distance of movements of aisle cranes and guided vehicles during transport, storage and retrieval operations; planning for non-interfering movements between aisle cranes and guided vehicles; reduction of the number of costly aisle cranes required without sacrificing storage capacity or introducing delays; and provision for "parking" inactive aisle cranes and guided vehicles in non-interfering locations.